Our goal is to contribute to the understanding of the contribution of structure and dynamics to the function of c-type cytochromes, in particular, and heme proteins, in general. Specifically, we propose to take advantage of our recently determined high resolution models for the solution of structures of reduced and oxidized cytochrome c to provide a basis for evaluation of theoretical treatments of the electron transfer solvent reorganization energy and the role of electrostatics in setting the redox midpoint; to quantitate the internal protein dynamics in the two redox states and relate this to the protein's promotion of electron transfer; to test working models for the structure of the bimolecular complex between cytochrome c and cytochrome bs; to examine the structural changes that occur upon association of cytochrome c with lipid; and to design and engineer a series of minimalist heme proteins, in order to resolve issues concerning the fundamental parameters governing interprotein electron transfer. We intend to examine in explicit detail the structural consequences of a number of single and multiple mutations of a c-type cytochrome molecule to probe the interaction between the global stability and folding behavior of the protein.